a gauntlet dropped in their laps.

[EUNJJUNG]

I'm reading an article called ""Drinking Age Has Simply Got to Go," Say Campus Riots" by Pamela White.
I have one question.

"Not surprisingly, police were frustrated and impatient. They'd tried the kid glove approach and had found a gauntlet dropped in their laps. The students were foul mouthed and furious."

Is the underlined phrase a idiomatic expression?
or Can i just interpret it literally?

[teechar]

No, it's meant metaphorically, not literally.
There are a couple of idioms involved here.
1- Throw down the gauntlet (here, we have a variation of it). That means to challenge someone to do something.
2- (Land) in someone's lap. That means someone is tasked/shouldered with a responsibility for something.

Note that I have moved your thread to our Idioms section.

[GoesStation]

Is the underlined phrase an idiomatic expression? (no question mark) or can i just interpret it literally?

Always capitalize the word "I". Don't capitalize other words except for proper nouns and the first word of a sentence. Use "an" before any word that begins with a vowel sound in spoken English.

[EUNJJUNG]

So then, this phrase 'They'd tried the kid glove approach' is metaphorically expression, too?

[GoesStation]

So then, this phrase, 'They'd tried the kid glove approach', is a metaphorically expression, too?

Yes. Kid-glove should be hyphenated there because it's a compound adjective.

[Charlie Bernstein]

It's called an extended metaphor. The writer has combined two common expressions.

To wear kid gloves (gloves made of the skin of a young goat) means to treat carefully.

To throw down the gauntlet means to challenge to a fight. In the middle ages, knights would throw a gauntlet (a big glove) at the feet of an adversary to (as we say today) call him out.

Used by themselves, the expressions are cliches and usually boring. Combining them in an extended metaphor makes for clever, lively writing.

[alexanderfinn]

One thing to avoid is called the 'mixed metaphor'. The sentences you gave are good because the writer is talking about gloves and keeps that image going, but let's say that you know the expression 'the boot is on the other foot' (which means that someone who was in a weak position has now become stronger than his/her opponent) and you tried to say

They threw down the gauntlet but the boot was now on the other foot.

It looks like it makes sense but it is very poor because first you used the image of a glove and then a boot in your metaphors. You shouldn't do that.

Native speakers make this mistake regularly. Yesterday a colleague said, 'we wanted a level playing field but we are being kept in the dark.' Do you have any idea what she wanted to say?